1. Field of the Invention
The present invention is directed to a process for pneumatic classification of mixtures of particulates as well as an apparatus and method for pneumatically classifying mixtures of particulates. More particularly, the present invention is directed to a process which classifies a mixture of particulates based primarily upon the aerodynamic support characteristics of the particulates, relative to each other. For example, a mixture of particulates may be classified by the process of the present invention into a fraction of particulates with high aerodynamic support characteristics and a fraction of particulates with low aerodynamic support characteristics. One example of an application of the process of the present invention is vacuuming up, then cleaning and subsequently classifying rock. The rock would be a mixture of particulates, including, but is not limited to, used landscape rock, used or fouled railroad ballast rock, and mining ore. Other applications include cleaning and/or classifying various mixtures of particulates such as mixtures including debris particulates, soils or ores, grains or food materials by or for pneumatic processing. Most particularly, the present invention is directed to a process for separating rock, such as used landscape rock or used railroad ballast rock or ores or lead particulates in soil or backstop materials from associated dirt or debris and/or other materials characterized by having a relatively higher or lower aerodynamic support characteristic and thereby cleaning the used landscape rock, used railroad ballast, or reclaiming the lead particulates or enriching or concentrating the ore, or cleaning grains or food materials.
2. Description of Related Art
There are many forms of decorative ground cover including mulch and decorative rock. Most forms of decorative ground cover deteriorate over time. Mulch decays, fades, and gets carried away by wind, water, animal foraging, and foot traffic. It frequently requires annual replenishment. Decorative rock is stable and lasts for years, but it is also prone to losing its aesthetic qualities. Silt, soil or both washes into the decorative rock from the adjacent ground and from downspout runoff. Decomposed leaves, seeds, sticks, grass trimmings, etc. eventually fill in the decorative ground cover. Over time weeds proliferate because of the accumulation of dirt. In arid areas the buildup of airborne sand is a problem. If located near roadways, there can be a problem with sand from snow removal.
Home owners have struggled to clean their landscape rock in a variety of ways including picking it up manually and cascading it over an improvised screening device while simultaneously hosing it off Such methods are cumbersome, tedious and involve handling the rock multiple times.
Commercial grounds keepers generally opt to just replace the rock, bringing in front-end loaders and other heavy equipment. This is expensive and prone to causing damage to existing lawns and shrubbery. Equipment is currently available for picking up landscape rock by means of a vacuum. Examples of such vacuum systems include U.S. Pat. No. 4,723,971 entitled “Industrial Vacuum Cleaner” issued on Feb. 9, 1988 to Ladislan B. Caldas, U.S. Pat. No. 4,735,639 entitled “Modular Industrial Vacuum Loading Apparatus for Ingesting and Collecting Debris and. Filtering Discharged Air” issued on Apr. 5, 1988 to Duncan Johnstone, the teachings of which are incorporated herein by reference in their entirety, as well as the industrial vacuum sold by Christianson Systems, Inc. of Blomkest, Minn. under the tradename “RockVac.” But, such vacuums do not clean the rock so it can be reused. The old rock, along with accompanying dirt and debris, is often disposed of in landfills, thereby exacerbating a growing ecological problem.
Accordingly, there is a need for an apparatus for cleaning landscape rock that can be made portable for on-site use, that is reliable, that is relatively easy to operate, that is capable of handling rock and debris that is accompanied by broad range of moisture contents, and that does not discharge an appreciable amount of dust to the environment.